[PATCH] D33540: [PM/ThinLTO] Port the ThinLTO pipeline (both components) to the new PM.

[Tim Shen via llvm-commits]

Clang sets lto::Config::UseNewPM. I suppose at somewheter in
lib/LTO/LTOBackend.cpp we should look at UseNewPM and
invoke buildThinLTOPreLinkDefaultPipeline, but I'm not sure where.

I don't expect any more change on Clang side, though.

On Tue, Jun 27, 2017 at 3:01 PM Chandler Carruth <chandlerc at google.com>
wrote:

> I thought Tim landed something that used this? But maybe misremembering. I
> don't think I have a Clang patch outstanding... +Tim Shen
> <timshen at google.com>
>
> On Tue, Jun 27, 2017 at 2:52 PM Teresa Johnson via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>>
>>
>> On Thu, May 25, 2017, 2:43 PM Chandler Carruth via Phabricator <
>> reviews at reviews.llvm.org> wrote:
>>
>>> chandlerc marked an inline comment as done.
>>> chandlerc added a comment.
>>>
>>> In https://reviews.llvm.org/D33540#764460, @tejohnson wrote:
>>>
>>> > > I hoisted the ThinLTO stop point pre-link above the partial inliner
>>> and the RPO function attr inference. Partial inlining isn't going to make
>>> the code smaller and it seems better to just do that once post-link.
>>> >
>>> > Added davidxl to comment on this change. It seems like doing some
>>> partial inlining during the pre-link for ThinLTO will have an effect on the
>>> importing. Also, it is pre-link (as well as post-link) in the old pass
>>> pipeline, so this would introduce an inconsistency between the pass
>>> pipelines. May be better to keep it in the same places, and evaluate the
>>> effect of removing it from the pre-link pass pipeline separately?
>>>
>>>
>>> Well, partial inliner isn't run at all yet. So my hope was it can get
>>> moved around later.
>>>
>>> I somewhat wanted to make the split line up with the simplification
>>> split that is already there in the pipeline. But if you feel strongly we
>>> need to keep these exactly the same, I can essentially copy the extra
>>> passes into the tail of the thinlto prelink stuff.
>>>
>>>
>>>
>>> ================
>>> Comment at: lib/Passes/PassBuilder.cpp:708
>>> +ModulePassManager
>>> +PassBuilder::buildThinLTOPreLinkDefaultPipeline(OptimizationLevel Level,
>>> +                                                bool DebugLogging) {
>>> ----------------
>>> tejohnson wrote:
>>> > I don't see this getting invoked.
>>> Yeah, the original patch had a change to Clang, but I wanted to get a
>>> submittable LLVM-focused version.
>>>
>>
>> Dehao just noticed that it still isn't be invoked, other than from the
>> manual pipeline setup for testing. Do you still have your clang side
>> changes around that you could submit? Or let me know if you prefer I add
>> that.
>> Teresa
>>
>>
>>> I'll add support for parsing these pipelines much like we support
>>> parsing 'default<O2>' and such so that we have some coverage of stuff.
>>>
>>>
>>> https://reviews.llvm.org/D33540
>>>
>>>
>>>
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